PURPOSE: To attain the miniaturization of a magneto-optical disk device and the reduction in thickness and also to present the device with small number of parts and simple construction.

CONSTITUTION: The magneto-optical disk device is provided with a cartridge holder 41 holding a cartridge wherein the disk is housed and an ejecting plate 50 capable of sliding along the cartridge holder 41, attached with a bias coil 51 impressing an external magnetic field on the recording range of disk. The ejecting plate 50 is driven by driving sources 52, 68 so as to slide along the cartridge holder 41. On the cartridge holder 41 and the ejecting plate 50, engaging pins 42, 43 and a cam groove 49 which arrange the disk to a spindle motor 55 while moving the cartridge holder 41 by the sliding of ejecting plate 50 and also arrange the bias coil 51 so as to be opposed to the disk, are respectively provided.